Camshaft phasers (“cam phasers”) for varying the timing of combustion valves in internal combustion engines are well known. A first element, known generally as a sprocket element, is driven by a chain, belt, or gearing from an engine's crankshaft. A second element, known generally as a camshaft plate, is mounted to the end of an engine's camshaft.
U.S. patent application Ser. No. 12/536,575; U.S. Provisional Patent Application Ser. No. 61/253,982; and U.S. Provisional Patent Application Ser. No. 61/333,775; which are commonly owned by Applicant and incorporated herein by reference in their entirety; disclose an eVCP camshaft phaser comprising a flat harmonic drive unit having a circular spline and a dynamic spline linked by a common flexspline within the circular and dynamic splines, and a single wave generator disposed within the flexspline. The circular spline is connectable to either of an engine camshaft or an engine crankshaft driven rotationally and fixed to a housing, the dynamic spline being connectable to the other thereof. The wave generator is driven selectively by an electric motor to cause the dynamic spline to rotate past the circular spline, thereby changing the phase relationship between the crankshaft and the camshaft.
The eVCP is attached to the camshaft with a bolt that extends axially through the eVCP and threadably engages the camshaft. In this way, the eVCP is clamped between the head of the bolt and the camshaft. While the eVCP is being attached to the camshaft, the housing of the eVCP is prevented from rotating by the chain, belt, or gearing which is connected to the crankshaft. As the bolt is tightened, friction is generated between the head of the bolt and the eVCP. This friction applies a torque that can cause undesired relative movement between the circular spline and the dynamic spline.
What is needed is an eVCP with means for temporarily fixing the circular spline to the dynamic spline in order to prevent relative rotation therebetween while the eVCP is being attached to said camshaft.